The track gauge

11. 10. 2023

The gauge of a railway indicates the internal distance between the two rails. The standard gauge differs from the broad gauge and the narrow gauge. This article explains when which gauge is used and why there are different gauges. 

Standard gauge: standardized gauge

With a width of 1,435 mm, standard gauge is the most widely used gauge in the world. The origin of its success dates back to 1822, when it was used to build the first public steam locomotive. From there, standard gauge quickly caught on in much of the world and is now most prevalent in most European countries, the Middle East, and North America and Africa, as well as China. Standard gauge is mainly used for passenger, regional and long-distance transport. Freight and high-speed trains, intercity and regional trains also travel on these tracks.

Roman chariots on English tracks

The question is: Why exactly 1,435 mm? The measurement was already used for the "tramroad" - these were railways in English coal mines. The further use of this measurement allowed already existing carts to use the newly built tracks. The origin of the odd gauge, however, lies even further in the past: it is said that standard gauge derives from the original specification for Roman chariots. With a measurement of 1,435 mm, these were exactly wide enough for two army horses to run in them without any problems.

If standard gauge was already prescribed as the standard gauge in Great Britain in 1846, 5,203 of a total of 5,575 kilometres of rail in Austria also run on standard gauge, while the remaining 372 kilometres are narrow gauge lines. 

Through tight curves and challenging terrain: the narrow gauge

As its name suggests, the narrow gauge differs from the standard gauge in that it has a smaller gauge. Most common are the metre gauge with a width of 1,000 mm or a gauge of 760 mm. The narrow gauge is used in regions and areas with difficult terrain: it can easily cope with sharp and narrow curves or steep descents. This includes, for example, the Mariazellerbahn.

Heavy freight on a large track: the broad gauge

Broad gauge, on the other hand, refers to a gauge that is larger than standard gauge and measures over 1,435 mm. The most common form is the Russian broad gauge with a measurement of 1,520 mm. It is the gauge with the largest network after the standard gauge. The larger the gauge, the greater the load-bearing capacity of the track. For this reason, the broad gauge is particularly suitable for transporting heavy goods over long distances. The Trans-Siberian Railway is probably the most famous broad-gauge railway.

Not all rails are the same

The different track gauges date back to a time when there were hardly any standardized specifications for track gauges and they were designed according to the wishes of the builder. In addition, for military and economic reasons, different track gauges were often deliberately chosen to prevent potential opponents or competing companies from using their own infrastructure to their advantage.

It was only later that the importance of a uniform gauge was recognized: it is significant for interoperability in rail transport and enables a seamless transition to another railway network without the need for reloading processes or gauge changes due to the exchange or conversion of the railway running gear. 

Today, the different track gauges no longer represent too significant an additional expense due to technical innovations that allow the running gear to be quickly changed or adapted to the gauge. 

Nevertheless, it is rather unlikely that new gauges will be introduced in the future. The focus is on further expanding the existing gauges. The standard gauge rail network in East Asia in particular is growing rapidly.